Delft University of Technology and Brown University pioneer technology for next-generation lightsails in space exploration

Researchers at TU Delft and Brown University have developed scalable nanotechnology-based lightsails that could support future advances in space exploration and experimental physics. Their research, published in Nature Communications, introduces new materials and production methods to create the thinnest large-scale reflectors ever made.

Lightsails are ultra-thin, reflective structures that use laser-driven radiation pressure to propel spacecraft at high speeds. Unlike conventional nanotechnology, which miniaturizes devices in all dimensions, lightsails follow a different approach. They are nanoscale in thickness—about 1/1000th the thickness of a human hair—but can extend to sheets with large dimensions.

Fabricating a lightsail as envisioned for the Starshot Breakthrough Initiative* would traditionally take 15 years, mainly because it is covered in billions of nanoscale holes. Using advanced techniques, the team, including first author and PhD student Lucas Norder, has reduced this process to a single day.

A new type of nanotechnology
‘This is not just another step in making things smaller; it’s an entirely new way of thinking about nanotechnology,’ explains Dr. Richard Norte, associate professor at TU Delft. ‘We’re creating high-aspect-ratio devices that are thinner than anything previously engineered but span dimensions akin to massive structures.’ The current prototype measures 60mm x 60mm and is 200 nanometres thick, covered in billions of nanosized holes. This represents a significant step forward in large-scale lightsail fabrication.

‘Other recent advancements in the field, such as from Caltech, have demonstrated nanoscale control over sail structures at micrometer scales, whereas our approach scales to centimeter-sized structures while maintaining nanoscale precision manufacturing.’ If scaled up, the lightsail made by Norte and colleagues would extend over the length of seven football fields with a thickness of only a millimetre. ‘It’s not just its high aspect ratio that makes this material special; it’s the simultaneous combination of large scale and nanoscale in the same material that makes it lightweight and reflective,’ says Norte.

The team combined state-of-the-art neural topology optimization techniques with cutting-edge fabrication methods to achieve this. ‘We have developed a new gas-based etch that allows us to delicately remove the material under the sails, leaving only the sail,’ Norte explains. ‘If the sails break, it’s most likely during manufacturing. Once the sails are suspended, they are actually quite robust. These techniques have been uniquely developed at TU Delft.’

‘Our work combines the latest advancements in optimisation to explore new ways to find unintuitive designs,’ says Dr. Miguel Bessa from Brown University. ‘By blending neural networks with topology optimization, we’ve created designs that push the boundaries of what’s possible in both nanophotonics and large-scale manufacturing.’

From picometers to centimetres to lightyears
The proposed lightsails leverage laser-driven radiation pressure to accelerate to astonishing velocities, enabling rapid interplanetary travel. For instance, probes propelled with the developed lightsails could, in theory, reach Mars in the time it takes for international mail to arrive. While such vast distances remain a goal for the future, recent studies have demonstrated that similar lightsails can currently be propelled over distances as small as picometers. Norte and his team are now preparing experiments to push the new membrane sails across distances measured in centimetres against Earth’s gravity. ‘It might not sound like a lot, but this would be 10 billion times farther than anything pushed with lasers so far.’

A universe of possibilities
Beyond space exploration, these materials open new possibilities for experimental physics. The ability to accelerate masses to high velocities offers unprecedented opportunities to study light-matter interactions and relativistic physics at macroscopic scales.

‘This EU-funded research places Delft at the forefront of nanoscale material science,’ Norte adds. ‘Now that we can make these lightsails as large as semiconductors can make wafers, we are exploring what we can do with today’s capabilities in nanofabrication, lasers, and design. In some ways, I think it might be just as exciting as missions beyond the solar system. What is remarkable to me is that creating these thin optical materials can open a window into fundamental questions such as; how fast can we actually accelerate an object. The nanotechnology behind this question is certain to open new avenues of interesting research.’

*Breakthrough Starshot Initiative

Currently, it would take around 10,000 years for our fastest rockets to reach even the nearest star outside the solar system. The Breakthrough Starshot Initiative, uniting thousands of researchers, seeks to reduce that journey to just 20 years. By developing ultra-light, laser-propelled spacecraft the size of microchips, the project envisions humanity's first interstellar exploration beyond the solar system. It is part of the Breakthrough Initiatives, a program funded by private investors. Starshot was launched by Yuri Milner and Stephen Hawking in 2016.